Maybe zone 6 (though in my old zone 6 garden I think it only lasted a year). Tasmanian Tiger is characias which is also one of the parents of Martinii and is generally only hardy to zone 7 though it can survive in sheltered well drained spots or in mild winters.

No, don't think it'd make it in zone 5. The hardier parent of the martinii cross, Euphorbia amygdaloides 'Purpurea' is said to only be hardy to zone 6 but it would still be a better risk and it's also a nice plant. There's a euphorbia called 'Garblesham Enchanter' which I haven't seen but it's rated as zone 5 hardy. It is semi-evergreen, according to the catalogues.

Euphorbia x martinii is hardy here. Mine has been in the garden nearly 10 years.
A friend of mine grew it successfully in Sault Ste. Marie.
I cannot speak to the hardiness of the new, variegated selection.
Euphorbia a. 'Purpurea' is also hardy here. E. 'Blackbird' did not make it, alas. Such a beauty. I've always assumed 'Tasmanian Tiger' would not make it through the winter here and have not tried it.
Others that are hardy are "First Blush','Bonfire', griffithii and griffithii 'Dixter', 'Excalibur', and E. niciana x nicaeensis 'Blue Haze'. I've tried others, but have lost track of them.
I assume good drainage is key.

I think ninamarie is probably closest :-) E. x martinii is listed hardy to zone 5 but that is not uniform for all selections. Variegated plants often tend to be a little less hardy and 'Ascot Rainbow' is listed and tested to 0F. And do not confuse hardiness with vigor: 'Tasmanian Tiger' was the first of the variegated forms of characias on the market and has proved to be a tempermental, short-lived selection. 'Glacier Blue' provides a similar look but with much improved vigor. 'Blackbird' appears to be another extremely attractive but very short-lived plant. I've replaced it with 'Ruby Glow'. All of these are fully hardy here but still offer mixed success, depending on specific cultivar, as outlined -- some new introductions just do not make the cut for long term garden success. 'Garblesham Enchanter' is also an amygdaloides cross and is no more hardy than its parent ( also a zone 5).

And yes, extremely good drainage, especially in cold or wet winter areas, is key.

btw, my 'Ascot Rainbow' is looking stunning now, having survived all winter in a container and a week in the teens in early December - lots of red/pink tones to the variegation and it is beginning to set buds.

wow, youall are a very impressive bunch and your articulate experiential info is much appreciated. i do grow a number of ppl lved euphorbs and just love them. But like those killer skimmia in England,I just gotta admire most of them from afar.

I think one valuable lesson I've learned, as a variegated foliage fan, is that w/ the new intros sold in the nurseries, it is likely better to wait a year before jumping in to purchase that gottahave pot.

th you again,
mindy

Interesting info folks, thanks. It sounds like I should be able to expand my Euphorbia collection -- love E. amygdaloides 'Purpurea', and E. polychomra (including 'Bonfire' and 'First Blush'), but I've always stayed away from the supposedly less hardy types, including E. x martinii.

Funny I was at one of my favorite little nurseries today and they had 3 huge pots of Euphorbia x martinii. Really beautiful specimens too. Made me think of this thread. If I had room in my garden I would have picked one up.

ah you devilish californian you, nursery hopping as we sit surrounded by snow!
best,
mindy

CPG, interestingly, while I can grow most hardy euphorbs in my climate without any concern (and many to the point where they become obnoxious pests!), none of the named poychromas have performed well here. Both 'Bonfire' and 'First Blush' petered out after their first season, although the species lived in my old garden for nearly 20 years -- go figure!! I am extremely fond of the martiniis as they develop into beautiful, dense, heavily blooming little mounds and have never reseeded. Can't say that about many of the rest, especially the characias. This species crosses with everything (or seems to) and reseeds like crazy, almost to the point of being invasive. But it has such a majestic size and early and long bloom season, it is hard to give up entirely.

Gardengal, that's a shame about 'Bonfire' and 'First Blush'. I would say both of them are in my top twenty - possibly top 10. They look beautiful from spring through fall without any maintenance. I have never watered them, or amended their soil or even cut them back.
Perhaps your climate is too damp.
By the way, I always loved my friend's description of E. x martinii in her garden. She said when in flower, it looked like a pimply faced teenager.

We're not as damp as many would think :-) I'd bet good money our annual rainfall is similar to or even less than yours. And E. characias is a Mediterranean species that loves drier conditions (a very xeric plant) but grows like a weed here. I'm not sure I can account for the named polychromas failure to thrive except that here they do not appear to be very vigorous plants.....even outside of my own garden, I've not seen these exist long term locally.

Walters Gardens in SW Michigan, the big perennial wholesaler, sells E. martinii Ascot Rainbow and lists it as z 5b and says it has been hardy in their trials. They are z 6 where they are and also have ideal growing conditions, sandy very well drained soils. I have found E. amygdaloides purpurea to be fairly hardy in SE MI z 5b but individual plants often dont last that well and it reseeds so it 'persists'.. Having said that I bought a flat of E.m. Ascot and I am going to plant them here this spring and see how they *do*....

I'm surprised to hear Euphorbia x martinii is hardy to zone 5. Even here in what is technically zone 8 it and a lot of other Euphorbias like characias, robbiae, and seguieriana niciciana get cut back now and then in a hard winter. The flower buds get killed and the foliage burnt and ugly until new growth fills in. This might be because of rapid temperature changes caused by Arctic blasts though-- maybe easing into very low temperatures gives these plants the edge they need to survive.

Boy, brody, that sure has not been my experience! I happen to have a rather strange attraction to all manner of hardy euphorbs and have grown dozens of them over the years and I have not experienced any kind of dieback of hardy euphorbs with winter cold. (Lack of vigor is another issue altogether :-)) Nor is it very obvious in local gardens.......many species of euphorbia are borderline invasive here (characias, robbiae, certainly cyparissias and myrsinites). Even semi-tender species like E. mellifera don't seem to have much problem :-)

Since you are further north and sometimes get that Fraser Valley cold, that may be an issue, but generally, if the drainage is very good, established, vigorous plants fly through PNW winters! Even the sudden, unusual single digit temps we experienced this past December. A drive through local neighborhoods right now will display various euphorbs - characias, robbiae and martinii primarily - in full bloom!